Pest profile

Hag Moth Caterpillar

Phobetron pithecium · Lepidoptera: Limacodidae[2]

The hag moth caterpillar resembles a dried leaf, yet all of its fleshy lobes carry stinging hairs.[1]

Hag moth caterpillar, a brown hairy caterpillar with curled fleshy lobes that resembles a dried leaf, on a leaf
Hag moth caterpillar, a brown hairy caterpillar with curled fleshy lobes that resembles a dried leaf, on a leaf. (c) Christopher Zacharias, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • It's brown with nine pairs of fleshy lobes, all bearing stinging hairs.[1]
  • It looks like a dried leaf, and it's also called the monkeyslug caterpillar.[1]

Look-alikes

Look-alikeHow to tell them apart
Saddleback caterpillarAnother slug caterpillar, green in the middle with a purple-centered saddle.[1]

Where it lives

UK Extension lists it among the more commonly encountered stinging caterpillars in Kentucky.[1]

US map: public records from 32 states since 1990 (GBIF).

Biology and life cycle

Slug caterpillars creep over leaves like slugs, with the head and legs hidden from above.[1]

It's usually seen feeding on the undersides of leaves on lower branches.[1]

Damage and signs

  • It feeds on oak, chestnut, dogwood, sassafras, ash and other trees and shrubs.[1]

Health risk

Its hollow stinging hairs release venom into the skin, causing anything from mild itching to pain, swelling and blistering.[1]

Control

Prevention

Don't brush it off or slap it with a bare hand; remove it carefully with a stick.[1]

Traps and physical control

For a single caterpillar, clip the leaf or stem and move it; preventive sprays aren't recommended.[1]

Common questions

What should I do if a caterpillar stings me?
Pull broken spines out with tape, wash with soap and water, use an ice pack, and see a doctor if the reaction is severe.[1]
Does the adult hag moth sting?
No; only the caterpillar stage has stinging hairs.[1]

Sources

  1. University of Kentucky Entomology (ENTFACT), “Stinging Caterpillars (ENTFACT-003).” entomology.mgcafe.uky.edu/ef003 (accessed 2026-10-06)
  2. iNaturalist, “Phobetron pithecium taxon page (order and family).” www.inaturalist.org/taxa/122254 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.